Variable reluctance sensors (VRSs) are commonly used to measure the angular position and/or speed of a moving or rotating ferromagnetic object. For example, they can be used to measure the angular position and/or speed of a rotating wheel having one or more teeth. One such application is the crankshaft of an automobile. For example, a toothed ferrous (iron based) wheel is mounted to the crankshaft and the VRS is used to sense each passing tooth during rotation of the crankshaft.
In such an application crankshaft position can be used to set engine timing for engine control including ignition and fuel injection timing and the like. The VRS typically includes a coil and biasing magnet positioned near the toothed wheel, in which each tooth passing by the VRS changes the magnetic flux which is converted to an electrical voltage induced in the coil. A VRS interface senses and conditions the electrical signal to derive timing parameters. In this manner, the rotating motion of the crankshaft is converted to an electronic signal which is used to determine the position and speed of the crankshaft.